1. Field of the Invention
The present invention relates to a power unit, and more particularly, to a power unit including a small air-cooled internal combustion engine suitable as a component of a portable or hand-held powered working machine.
2. Description of the Related Art
A power unit including a small air-cooled internal combustion engine is widely used as a power source for a portable or hand-held powered working machine.
In the power unit, it is a necessity that the internal combustion engine be sufficiently cooled. Ordinarily, a magneto rotor fixed on a crank shaft functions as a fan by including thereon fan blades such that the internal combustion engine is cooled by air supplied to the periphery of a cylinder thereof. Japanese Examined Utility Model Application Publication No. 2-10299 discloses that fan blades may also be disposed on a start pulley that is part of a recoil starter, in addition to fan blades disposed on the magneto rotor.
However, in that prior art, the fan blades disposed on the start pulley are disposed in such a way so as to cool the recoil starter, but not the internal combustion engine.